This invention relates to novel herbicidal compounds having the formula ##STR2## in which X is chloro, bromo, trifluoromethyl, methyl or ethyl; R.sub.1 is hydrogen or C.sub.3 -C.sub.5 alkenyl; and R.sub.2 is (a) C.sub.3 -C.sub.5 alkenyl if R.sub.1 is C.sub.3 -C.sub.5 alkenyl; (b) C.sub.3 -C.sub.5 alkyl, C.sub.3 -C.sub.5 alkenyl or C.sub.3 -C.sub.6 alkynyl if X is chloro, methyl, ethyl or trifluoromethyl and R.sub.1 is hydrogen; and (c) C.sub.1 -C.sub.5 alkyl, C.sub.3 -C.sub.5 alkenyl or C.sub.3 -C.sub.6 alkynyl if X is bromo and R.sub.1 is hydrogen.
These compounds have been found to exhibit herbicidal properties.
The term "C.sub.3 -C.sub.5 alkyl" includes straight chain and branched chain substituents of this type, with branched chain substituents being preferred. The term "C.sub.3 -C.sub.5 alkenyl" includes substituents of this type having either straight or branched chains and having one or two double bonds. A preferred substituent of this type is allyl. The term "C.sub.3 -C.sub.6 alkynyl" includes substituents of this type having a straight or branched chain and at least one triple bond. A preferred member of this group is 1,1-dimethyl-2-propynyl, also called 1,1-dimethylpropargyl.
The compounds of this invention have been found to be active herbicides; that is the compounds have been found to be herbicidally active against various species of weeds. In the broadest sense, the term "weeds" refer to plants which grow in locations in which they are not desired. As will be seen from the data which follows, these compounds show various activities as pre-emergence and/or post-emergence herbicides. In some cases they have been found to show particular activity against certain weed species.
This invention, therefore, also relates to a method of controlling undesirable vegetation comprising applying to such vegetation a herbicidally effective amount of a compound as described herein, and also relates to herbicidal compositions of matter comprising a herbicidally effective amount of a compound as described herein plus an inert diluent or carrier suitable for use with herbicides.
As used herein, the term "herbicide" means a compound which controls or modifies the growth of plants, particularly of undesirable plants. By the term "herbicidally effective amount" is meant an amount of a compound which causes a controlling or modifying effect on the growth of plants. The term "plants" is meant to include germinant seeds, emerging seedlings and established vegetation including roots and above ground portions. Such modifying and controlling effects include all deviations from natural development.
In general, the compounds can be prepared by the reaction of the appropriate 2-(3-substituted phenoxy) nicotinoyl chloride with an amine: ##STR3## in which X, R.sub.1, and R.sub.2 are as previously defined. The reaction is carried out in the presence of an acid acceptor such as caustic, an additional equivalent of the reacting amine or another amine (triethylamine is preferred). Reaction temperatures may range from about 0.degree. to about 100.degree. C., at atmospheric pressure. Any of a number of solvents may be used, for instance, methylene chloride, diethyl ether, benzene and, preferably, toluene. The product may be recovered by first removing the by-product salt or amine salt with water, then recovering the product from the organic layer by conventional means.
The nicotinoyl chlorides are prepared from the corresponding carboxylic acids by the conventional technique of reacting the acid with a suitable chlorinating agent such as phosgene, PCl.sub.3, PCl.sub.5, or, preferably, thionyl chloride. Temperatures may range from about 25.degree. to about 110.degree. C. Solvents such as those mentioned above may be used. The acids may be prepared by reacting a meta-substituted phenol with 2-chloronicotinic acid, as described by Villani, et al., J. Medicinal Chemistry 18, 1 (1975).